2024 NYJC H1 Chem 8873 P2 Answers

[Turn over NANYANG JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 1 CANDIDATE NAME CLASS TUTOR’S NAME CHEMISTRY 8873/02 Paper 2 Structured Questions 9 September 2024 2 hours Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces provided at the top of this page. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 /9 2 /8 3 /9 4 /10 5 /15 6 /9 7/8 /20 Total /80 This document consists of 26 printed pages. H

2 H1 Chemistry 8873/02 NYJC J2/24 PX [Turn Over For Examiner's Use Section A Answer all questions in the spaces provided. 1 This question is about the chemistry of sodium and oxygen. (a) (i) Define the term first ionisation energy. The first ionisation energy of an element is the amount of energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of singly-charged gaseous cations. [1] X(g) → X+(g) + e ΔH = 1st I.E. (ii) Explain the following comparisons of ionisation energies. • The first ionisation energy of Na (494 kJ mol –1) is very much lower than that of oxygen (1310 kJ mol–1). • The second ionisation energy of Na (4 560 kJ mol –1) is very much higher than its first ionisation energy (494 kJ mol–1). 1st I.E. of Na is lower than that of O • As Na has more protons than O, nuclear charge is higher in Na. • As Na has one more electron shell than O, shielding effect increases significantly in Na. • The outermost electron is further away from the nucleus in Na. • The net attraction between the nucleus and outermost electron decreases in Na and less energy is required to remove the outermost electron. 4 points [2], 2 points [1] 2nd I.E. of Na is higher than its 1st I.E. A lot more energy is needed to remove a negatively charged electron from a positively charged Na+ ion due to stronger electrostatic attraction. [1] OR There are less electrons than protons in Na+. The repulsion/shielding effect among the remaining electrons decreases and they are also more strongly attracted to the constant positive nuclear charge . Hence more energy is required to overcome the stronger attraction to remove the outermost electron. [1] OR For 2nd IE, the electron to be removed from N